Civil and Environmental Engineering, University of Western Ontario, London, ON N6A 5B9, Canada.
Civil and Environmental Engineering, University of Western Ontario, London, ON N6A 5B9, Canada; Chemical and Biochemical Engineering, University of Western Ontario, London, ON N6A 5B9, Canada.
Sci Total Environ. 2022 Mar 10;811:151373. doi: 10.1016/j.scitotenv.2021.151373. Epub 2021 Nov 5.
Anammox retention, which is crucial for successful nitrogen removal because of slow growth, is still a major challenge. Fixed film processes or gel-immobilization techniques can minimize biomass washout. However, the detachment mechanisms from gel-immobilized beads are still unclear. Despite the widely known advantages of fluidized bed reactor (FBR) with respect to biomass retention, the technology has not been investigated for anammox processes, and thus, the current study evaluated the feasibility of using immobilized anammox gel beads as a carrier media in anammox fluidized bed reactor (AFBR), with a particular focus on understanding detachment mechanisms. The study optimized the packing ratio in AFBR and compared holed and non-holed beads. The optimum packing ratio (on a volumetric basis) was 30% (v/v) with a nitrogen removal rate (NRR) of 0.40 kg N/m-d at a volumetric nitrogen loading rate (NLR) of 0.51 kg N/m-d. Biomass detachment rates increased linearly with specific anammox activity (SAA). The fluidized bed reactor employing holed (more porous) anammox gel beads (HFBR) exhibited 20% lower biomass detachment rates than the non-holed fluidized bed reactor (NHFBR). Moreover, the HFBR achieved a maximum NRR of 0.81 kg N/m-d at NLR of 1.01 kg N/m-d after 35 days without operational problems, whereas the NHFBR with non-holed anammox gel beads failed after 30 days. The hindrance to diffusion of the generated nitrogen gas was the main mechanism of beads breakup and biomass washout, and thus, the sustainability of the beads hinges on increased external porosity. Therefore, developing microporous gel beads is critical for achieving a high rate stable anammox process that overcomes the limitations of the current technologies.
由于生长缓慢，厌氧氨氧化菌的保留对于成功脱氮至关重要，但这仍然是一个主要挑战。固定膜工艺或凝胶固定化技术可以最大限度地减少生物量流失。然而，凝胶固定化珠的脱落机制仍不清楚。尽管流化床反应器（FBR）在生物量保留方面具有广泛的优势，但该技术尚未用于厌氧氨氧化工艺，因此，本研究评估了将固定化厌氧氨氧化凝胶珠用作厌氧氨氧化流化床反应器（AFBR）中的载体介质的可行性，特别关注了解脱落机制。该研究优化了 AFBR 中的填充率，并比较了有孔和无孔珠。在体积氮负荷率（NLR）为 0.51 kg N/m-d 时，最佳填充率（基于体积）为 30%（v/v），氮去除率（NRR）为 0.40 kg N/m-d。生物量脱落率随比厌氧氨氧化活性（SAA）呈线性增加。与无孔流化床反应器（NHFBR）相比，采用多孔（更具多孔性）厌氧氨氧化凝胶珠的流化床反应器（HFBR）的生物量脱落率低 20%。此外，HFBR 在 35 天内无需运行问题即可在 NLR 为 1.01 kg N/m-d 时达到 0.81 kg N/m-d 的最大 NRR，而使用无孔厌氧氨氧化凝胶珠的 NHFBR 在 30 天后失效。生成的氮气扩散的阻碍是珠粒破裂和生物量流失的主要机制，因此，珠粒的可持续性取决于增加的外部孔隙率。因此，开发微孔凝胶珠对于实现克服当前技术限制的高速率稳定厌氧氨氧化过程至关重要。
